This invention relates to a coupling assembly for an internal combustion engine and, more particularly, to an assembly for affecting a fluid coupling between the output shaft of the engine and a cooling fan for the engine.
Cooling fans have long been used for cooling internal combustion engines. In some arrangements of this type, the cooling fan is driven by a pulley or the like which is directly connected to the main output shaft of the engine. As a result, the angular velocity of the fan increases in direct proportion to the increase in engine speed. Since the intensity of sound produced by the fan is in proportion to the sixth power of its velocity, it can be appreciated that the noise generated by the fan can reach very loud levels with corresponding increases in the engine speed.
It has been suggested to employ a fluid coupling between the engine output shaft and the fan in order to suppress the proportional increases in the fan velocity after a predetermined engine speed has been achieved in order to minimize the noise generated by the fan. However, in these arrangements, the fan velocity and resultant noise are reduced only during normal operation of the engine and are not reduced if the engine rotation is rapidly accelerated.